In one form of a fluid flow control valve, a poppet is movably positioned in a stationary valve seat to open or close the valve. The poppet is provided with a pilot valve chamber connecting an axial bore which is selectively opened or closed by a pilot valve. A reciprocally movable solenoid plunger is operatively associated with the pilot valve for positioning the pilot valve. The pilot valve is spring biased to either a normal open or closed position. A solenoid coil controllably positions the plunger to move the pilot valve to an actuated position as by overcoming the bias of the spring.
A problem arises in such cartridge valves in that it is desirable at times to operate the valve manually, such as to close or open the valve in the event of failure of the solenoid, or when performing troubleshooting. It is also desirable that with operating the valve manually, the valve be provided with a fool-proof system to enable automatic return to the non-overridden position.
For a valve manufacturer problems arise owing to the various different configurations used in a given line of solenoid cartridge valves. For example, the valves can be normally open or normally closed, fast response or high flow type, as well as high pressure or low pressure. Usually when going from one type valve to another, it is necessary to use different parts in each type owing to the distinct operational requirements of each. Such requirements necessitate the stocking of greater numbers of parts and purchasing in less quantities so that manufacturing and purchasing economies of scale are less than ideal.
The present invention is intended to overcome one or more of the problems as set forth above.